linux-kernel - Re: [PATCH v1] gpio: pca953x: fix IRQ storm on system wake up

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Message-ID: <CAMRc=Me15MyNJiU9E-E2R9yHZ4XaS=zAuETvzKFh8=K0B4rKPw@mail.gmail.com>
Date: Thu, 3 Apr 2025 15:56:37 +0200
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Andy Shevchenko <andriy.shevchenko@...el.com>
Cc: Geert Uytterhoeven <geert@...ux-m68k.org>, Linus Walleij <linus.walleij@...aro.org>, 
	Francesco Dolcini <francesco@...cini.it>, Bartosz Golaszewski <bartosz.golaszewski@...aro.org>, 
	Emanuele Ghidoli <emanuele.ghidoli@...adex.com>, linux-gpio@...r.kernel.org, 
	linux-kernel@...r.kernel.org, Marek Vasut <marek.vasut@...il.com>, 
	stable@...r.kernel.org, Francesco Dolcini <francesco.dolcini@...adex.com>
Subject: Re: [PATCH v1] gpio: pca953x: fix IRQ storm on system wake up

On Thu, Apr 3, 2025 at 3:54 PM Andy Shevchenko
<andriy.shevchenko@...el.com> wrote:
>
> +Cc: Geert
>
> On Thu, Apr 03, 2025 at 02:07:05PM +0200, Bartosz Golaszewski wrote:
> > On Wed, 26 Mar 2025 18:38:38 +0100, Francesco Dolcini wrote:
>
> > > If an input changes state during wake-up and is used as an interrupt
> > > source, the IRQ handler reads the volatile input register to clear the
> > > interrupt mask and deassert the IRQ line. However, the IRQ handler is
> > > triggered before access to the register is granted, causing the read
> > > operation to fail.
> > >
> > > As a result, the IRQ handler enters a loop, repeatedly printing the
> > > "failed reading register" message, until `pca953x_resume` is eventually
> > > called, which restores the driver context and enables access to
> > > registers.
>
> [...]
>
> > Applied, thanks!
>
> Won't this regress as it happens the last time [1]?
>
> [1]: https://lore.kernel.org/linux-gpio/CAMuHMdVnKX23yi7ir1LVxfXAMeeWMFzM+cdgSSTNjpn1OnC2xw@mail.gmail.com/
>

Ah, good catch. I'm wondering what the right fix here is but don't
really have any ideas at the moment. Any hints are appreciated.

For now, I'm dropping it.

Bart